Benign prostate hypertrophy, also known as benign prostate hyperplasia (BPH) commonly afflicts men beginning at age 50. The prostate swells and presses on the urethra, making urination difficult and uncomfortable. In addition, it may cause urination urgency. Also afflicting older men is prostate cancer which may metastasize and cause death. Early treatment can reduce the risks of death from prostate cancer.
Both prostate enlargement and prostate cancer may be treated with heat treatments such as hyperthermia or thermotherapy. As described in co-pending U.S. app. Ser. No. 08/629,650, filed Apr. 9, 1996, a stent may serve the dual purpose of acting as a heat source for the thermotherapy procedures, as well as acting to hold the urethra open after therapy to temporarily prevent blockage due to swelling and prostate tissue sloughing. Additionally, a stent may be implanted temporarily while the patient awaits more aggressive surgery or treatment. Rather than implantation after thermotherapy, a stent may be implanted temporarily after cryosurgery or hypothermia. Finally, a stent may be implanted as a primary treatment.
Given the number of therapies employing urethral stents, there is a need in the art for improved stent delivery systems. Eum, U.S. app. Ser. No. 09/063,118, filed Apr. 20, 1998, and incorporated herein by reference, discloses a stent delivery system comprising a catheter with an anchoring mechanism at its distal end that is placed within the bladder. The stent is displaced proximally on the catheter a predetermined distance from the anchor. This ensures that the stent does not affect the bladder sphincter. Placement of a stent within the bladder sphincter could lead to incontinence and other problems. Because the anchoring mechanism must be placed within the bladder, such a stent delivery system requires a flexible endoscope. Many doctors, however, are equipped only with standard rigid urological endoscopes, which cannot maneuver through the prostatic urethra into the bladder. Thus, there is a need in the art for improved stent delivery systems that can accurately and conveniently implant a stent in the prostatic urethra using conventional rigid urological endoscopes.
The stent delivery systems described below permit placement of a stent in the urethra. The devices efficiently implant a stent into the prostatic urethra under direct vision. The invention has two main embodiments.
In the first embodiment, the invention comprises a bi-petaled insertion catheter including an outer sheath, a peel-away sheath adapted to cover a stent mounted within the outer sheath, and an inner sheath covering a proximal portion of the stent. Upon inserting the catheter into the prostatic urethra, a clinician will guide the distal end of the catheter under direct vision proximally to the bladder sphincter using an endoscope inserted within the inner sheath. Additionally, the clinician could guide the distal end of the catheter using ultrasonic or x-ray imaging. The outer sheath is then proximally displaced, exposing the distal end of the peel-away sheath. The distal end of the stent expands and separates longitudinal slits within the exposed portion of the peel-away sheath and begins gripping the urethral wall. By distally displacing the inner sheath with respect to the peel-away sheath and the outer sheath, a clinician distally displaces the distal portion of the stent from the peel-away sheath. Thus exposed, the distal portion of the stent grips the prostatic urethra, allowing the clinician to then fully separate the peel away sheath along its longitudinal slits and retract the peel-away sheath and the inner sheath from the stent to complete the stent deployment.
In a preferred second embodiment, the invention comprises a single-petaled catheter including an outer sheath and an inner tubular member. The inner tubular member ends distally in an elongated tongue having an arcuate cross section. The clinician guides the distal end of the catheter into position using an endoscope inserted within the lumen of the inner tubular member and/or using ultrasonic or x-ray imaging. After positioning the catheter, the clinician proximally displaces the outer sheath to expose the tongue of the inner tubular member. The distal end of the stent expands against the now exposed tongue to begin gripping the urethral wall. When satisfied with the final stent position, the clinician proximally withdraws the inner tubular member away from the stent, using the distal end of the outer sheath to prevent proximal displacement of the stent. The outer sheath may then be withdrawn, completing the stent deployment.